Premium
C‐ fos mRNA is Spontaneously Induced in the Rat Brain During the Activity Period of the Circadian Cycle
Author(s) -
GrassiZucconi G.,
Menegazzi M.,
Prati A. Carcereri,
Bassetti A.,
Montagnese P.,
Mandile P.,
Cosi C.,
Bentivoglio M.
Publication year - 1993
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1993.tb00960.x
Subject(s) - circadian rhythm , period (music) , wakefulness , endocrinology , medicine , c fos , basal (medicine) , nocturnal , darkness , morning , biology , electroencephalography , neuroscience , gene expression , physics , biochemistry , gene , botany , acoustics , insulin
The basal expression of the proto‐oncogene c‐ fos was studied by Northern blot analysis in different regions of the rat brain during 24 h. A striking spontaneous oscillation of c‐ fos mRNA expression was detected in animals kept in basal conditions with a 12 h light/12 h dark cycle. In these animals c‐ fos mRNA was just detectable during the rest hours (morning through afternoon), and was high during the activity hours (night). The periodicity of this oscillation persisted and became free‐running when the animals were exposed for 6 consecutive days to constant light or darkness. It was thus demonstrated that the fluctuation of c‐ fos expression is circadian and is not created by the light‐dark cycle, but the latter exerts a synchronizing effect. The oscillation of c‐ fos mRNA was modified by manipulations of the rest‐activity cycle. In particular, the fluctuation observed in basal conditions was inverted, keeping the animals awake during the rest hours (diurnal) and allowing them to sleep in the activity period (nocturnal). These data indicated a close relationship between the oscillation of c‐fos expression and the rest‐activity cycle. Finally, electroencephalographic (EEG) monitoring was performed under behavioural control for 3 h before the animals were killed. These experiments confirmed that, irrespective of the time of day, the EEG pattern typical of a state of sleep (including both slow waves and paradoxical sleep) was associated with low or undetectable c‐ fos levels, whereas the protracted EEG desynchronization corresponding to wakefulness was associated with high c‐ fos expression. Altogether these results indicate that c‐ fos mRNA undergoes during the circadian cycle spontaneous oscillations related to the activation of genomic expression subserving the behavioural and electrical correlates of wakefulness. On the other hand, the behavioural and electrical correlates of sleep are associated with low c‐ fos expression.